Changes in soluble proteins during foot-pad development in Sarcophaga bullata

Changes in total and soluble protein in giant foot-pad cells of Sarcophaga bullata pupae follow a biphasic curve with maxima at stages 3 and 9. These polytene cells undergo a sequence of well-defined morphological changes involving deposition of adult cuticle. Alterations in soluble protein species with increases and decreases in concentration, as well as gain and loss of individual components, are associated with developmental events. Molecular heterogeneity and developmental changes of DOPA oxidase, acid phosphatase, and malate dehydrogenase are evident in foot-pad cells. ¹⁴C-leucine incorporation into foot-pad protein is high at stages 5 to 6. These data are discussed in terms of their relationship to cell morphology, function, and chromosome puffing activities.